AWS Lambda with Amazon EventBridge Scheduler is the most cost-effective solution because the workload is short, periodic, and does not require a continuously running server. The Python script runs every 30 minutes and takes only about 20 seconds, so paying for EC2 capacity that remains mostly idle would waste money. Lambda charges based on requests and execution duration, which fits this intermittent workload well. EventBridge Scheduler can invoke the Lambda function on a recurring schedule. Provisioned concurrency is unnecessary because this is not a latency-sensitive user-facing workload. API Gateway is also unnecessary because the script does not need an HTTP endpoint. Spot Instances reduce EC2 cost but still add instance management and interruption risk.